Apparatus and method for estimating carrier-to-interference and noise ratio in a communication system

ABSTRACT

An apparatus and method for estimating a Carrier-to-Interference and Noise Ratio (CINR) in a communication system are provided. In the apparatus and method a signal having a traffic allocation available area that includes a preamble allocation available area is generated by Fast Fourier Transform (FFT)-processing a received symbol, power values of preamble tones included in the preamble allocation available area are calculated, a carrier power value is calculated using the power values of the preamble tones, a partial noise-interference power value is calculated using power differences between the preamble tones and power values of remaining tones other than the preamble tones, a noise power value is calculated using power values of tones included in a noise power estimation area being an area except for the preamble allocation available area in the traffic allocation available area, and the CINR is calculated using the carrier power value, the partial noise-interference power value, and the noise power value.

PRIORITY

This application claims the benefit under 35 U.S.C. §119(a) of a Koreanpatent application filed in the Korean Intellectual Property Office onMay 28, 2007 and assigned Serial No. 2007-51741, the entire disclosureof which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a communication system. Moreparticularly, the present invention relates to a method and apparatusfor estimating Carrier-to-Interference and Noise Ratio (CINR) in acommunication system.

2. Description of the Related Art

Future-generation communication systems are under development to provideservices capable of high-speed, large-data transmission and reception toMobile Stations (MSs). An example of a future-generation communicationsystem is an Institute of Electrical and Electronics Engineers (IEEE)802.16 system.

The IEEE 802.16 communication system uses Orthogonal Frequency DivisionMultiplexing (OFDM) that offers the benefits of Inter-SymbolInterference (ISI) cancellation through a simple equalizer, robustnessagainst noise, and high frequency use efficiency.

The IEEE 802.16 communication system adopts Adaptive Modulation andCoding (AMC) to efficiently transmit data. AMC is a transmission schemein which an optimal Modulation and Coding Scheme (MCS) level isadaptively selected from among preset MCS levels according to a changein a channel environment and data is encoded and modulated at theselected MCS level prior to transmission.

For implementation of AMC, an MS feeds back channel status informationabout a radio channel to a Base Station (BS). Specifically, the MSestimates the CINR of a received signal as the channel statusinformation and feeds back the CINR estimate to the BS.

If the BS uses a self-configurable technology, it determines optimaloperation parameters based on channel status information about signalsreceived from neighbor BSs. The self-configurable technology is atechnology for automatically setting operation parameters such as atransmit power and a Frequency Assignment (FA) to efficiently transmitdata. To do so, the BS estimates the CINRs of the received signals asthe channel status information about the neighbor BSs and determinesoptimal operation parameters based on the estimated CINRs.

The CINR of a BS can be estimated using a preamble signal.

With reference to FIGS. 1 and 2, the manner in which an MS estimates aCINR will be described. FIG. 1 illustrates a conventional method forallocating a preamble signal to subcarriers in a BS.

The BS transmits a preamble signal to the MS in the first of OFDMsymbols that form a downlink frame. The preamble signal is a sync signalto establish synchronization between the BS and the MS. Morespecifically, the BS defines a preamble allocation available area in thefirst OFDM symbol and maps preamble tones that form a preamble signal topart or all of the subcarriers of the preamble allocation available areaaccording to a preset preamble allocation scheme. Then the BS eliminatesthe remaining subcarriers, except for the subcarriers having thepreamble tones, and transmits the preamble signal to the MS.

The preamble allocation can be considered in three ways depending on theposition of the preamble signal in the OFDM symbol. As illustrated inFIG. 1, preamble tones are allocated every three subcarriers, startingfrom subcarrier 0 in the preamble allocation available area (a segment 0scheme 100), every three subcarriers, starting from subcarrier 1 in thepreamble allocation available area (a segment 1 scheme 102), or everythree subcarriers, starting from subcarrier 2 in the preamble allocationavailable area (a segment 2 scheme 104).

The BS transmits the preamble signal to the MS in the OFDM symbol usingone of the above three preamble allocation schemes. The MS then receivesthe OFDM symbol and estimates the CINR of the OFDM symbol using thepreamble signal. With reference to FIG. 2, a conventional operation forestimating the CINR in the MS will be described below.

Referring to FIG. 2, the MS includes an Analog-to-Digital Converter(ADC) 200, a Fast Fourier Transform (FFT) processor 202, and a CINRestimator 214. The CINR estimator 214 has a noise power estimator 204,an interference power estimator 206, a carrier power estimator 208, apreamble code generator 210, and a CINR calculator 212.

The ADC 200 converts a preamble signal received through an antenna to adigital preamble signal. The FFT processor 202 generates a digital FFTpreamble signal by FFT-processing the digital preamble signal receivedfrom the ADC 200 on an OFDM symbol basis.

The noise power estimator 204 estimates a noise power value using thedigital preamble signal received from the ADC 200. The preamble codegenerator 210 generates a preamble code with which to demodulate thedigital FFT preamble signal. The carrier power estimator 208 receivesthe digital FFT preamble signal from the FFT processor 202 and thepreamble code from the preamble code generator 210, demodulates thedigital FFT preamble signal using the preamble code, and estimates acarrier power value using the demodulated digital preamble signal.

The interference power estimator 206 calculates the signal power valueof the digital FFT preamble signal received from the FFT processor 202,calculates an interference power value using the signal power value, thenoise power value, and the carrier power value. Herein, the interferencepower estimator 206 can calculate the interference power value bysubtracting the carrier power value and the noise power value from thesignal power value. The CINR calculator 212 calculates a CINR using thenoise power value, the interference power value, and the carrier powervalue.

In the above-described conventional CINR estimation method, the carrierpower value and the noise power value are subtracted from the signalpower value. However, when the preamble signal has no interference orthe magnitude of the interference is negligibly small, there is an errorbetween the interference power value calculated by the CINR estimator214 and a real interference power value. As a consequence, the estimatedCINR is less accurate.

Moreover, the noise power is estimated using the time-domain preamblesignal in the conventional CINR estimation method. If an actual CINR ofthe preamble signal is large in a multi-path environment, there is anerror between the noise power value calculated by the CINR estimator 214and a real noise power value. As a consequence, the estimated CINR isless accurate.

SUMMARY OF THE INVENTION

An aspect of the present invention is to address at least theabove-mentioned problems and/or disadvantages and to provide at leastthe advantages described below. Accordingly, an aspect of the presentinvention is to provide a method and apparatus for estimating a CINR ina communication system.

Another aspect of the present invention provides a method and apparatusfor accurately estimating an interference power value, even when thereis no interference or when the magnitude of the interference isnegligibly small in an actual preamble signal in a communication system.

A further aspect of the present invention provides a method andapparatus for accurately estimating a noise power value, even when anactual CINR of a preamble signal is large under a multi-path environmentin a communication system.

In accordance with an aspect of the present invention, a method forestimating a CINR in a communication system is provided. The methodincludes generating a signal, including a traffic allocation availablearea for allocating a traffic signal and a preamble allocation availablearea for allocating a preamble signal, by FFT-processing a received OFDMsymbol, the traffic allocation available area comprising the preambleallocation available area, calculating power values of preamble tonesincluded in the preamble allocation available area, calculating acarrier power value using the power values of the preamble tones,calculating a partial noise-interference power value using powerdifferences between the preamble tones and power values of remainingtones other than the preamble tones, calculating a noise power valueusing power values of tones included in a noise power estimation area,the power estimation area being an area of the traffic allocationavailable area other than the preamble allocation available area, andcalculating the CINR using the carrier power value, the partialnoise-interference power value, and the noise power value.

In accordance with another aspect of exemplary embodiments of thepresent invention, an apparatus for estimating a CINR in a communicationsystem is provided. The apparatus includes an FFT processor forgenerating a signal, including a traffic allocation available area forallocating a traffic signal and a preamble allocation available area forallocating a preamble signal, by FFT-processing a received symbol, thetraffic allocation available area comprising the preamble allocationavailable area, a carrier power estimator for calculating power valuesof preamble tones included in the preamble allocation available area andfor calculating a carrier power value using the power values of thepreamble tones, a partial noise-interference power estimator forcalculating a partial noise-interference power value using powerdifferences between the preamble tones and power values of remainingtones other than the preamble tones, a noise power estimator forcalculating a noise power value using power values of tones included ina noise power estimation area, the power estimation area being an areaof the traffic allocation available area other than the preambleallocation available area, and a CINR calculator for calculating theCINR using the carrier power value, the partial noise-interference powervalue, and the noise power value.

In accordance with a further aspect of exemplary embodiments of thepresent invention, a method for estimating interference and noise in acommunication system is provided. The method includes generating asignal, including a traffic allocation available area for allocating atraffic signal and a preamble allocation available area for allocating apreamble signal, by FFT-processing a received symbol, the trafficallocation available area comprising the preamble allocation availablearea, calculating a partial noise-interference power value using powerdifferences between preamble tones included in the preamble allocationavailable area and power values of remaining tones other than thepreamble tones in the preamble allocation available area, calculating anoise power value using power values of tones included in a noise powerestimation area, the power estimation area being an area of the trafficallocation available area other than the preamble allocation availablearea, and calculating the interference and noise using the partialnoise-interference power value and the noise power value.

In accordance with still another aspect of exemplary embodiments of thepresent invention, an apparatus for estimating interference and noise ina communication system is provided. The apparatus includes an FFTprocessor for generating a signal, including a traffic allocationavailable area for allocating a traffic signal and a preamble allocationavailable area for allocating a preamble signal, by FFT-processing areceived symbol, the traffic allocation available area comprising thepreamble allocation available area, a partial noise-interference powerestimator for calculating a partial noise-interference power value usingpower differences between preamble tones included in the preambleallocation available area and power values of remaining tones other thanthe preamble tones in the preamble allocation available area, a noisepower estimator for calculating a noise power value using power valuesof tones included in a noise power estimation area, the power estimationarea being an area of the traffic allocation available area other thanthe preamble allocation available area, and a interference and noisecalculator for calculating the interference and noise using the partialnoise-interference power value and the noise power value.

Other aspects, advantages, and salient features of the invention willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of certainexemplary embodiments of the present invention will be more apparentfrom the following description taken in conjunction with theaccompanying drawings, in which:

FIG. 1 illustrates a conventional method for allocating a preamblesignal to subcarriers in a BS;

FIG. 2 is a block diagram of an MS for estimating a CINR according to aconventional technology;

FIG. 3 is a block diagram of an MS according to an exemplary embodimentof the present invention;

FIG. 4A illustrates an operation for estimating a noise-interferencepower value in the MS according to an exemplary embodiment of thepresent invention;

FIG. 4B illustrates a noise power estimation area used for estimating anoise power in the MS according to an exemplary embodiment of thepresent invention;

FIG. 5 is a flowchart illustrating an operation for estimating a CINR inthe MS according to an exemplary embodiment of the present invention;and

FIG. 6 is a compilation of graphs illustrating the standard deviationsand means of CINRs measured by the MS according to an exemplaryembodiment of the present invention.

Throughout the drawings, the same drawing reference numerals will beunderstood to refer to the same elements, features and structures.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of exemplaryembodiments of the invention as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the embodiments described hereincan be made without departing from the scope and spirit of theinvention. Also, descriptions of well-known functions and constructionsare omitted for clarity and conciseness.

Exemplary embodiments of the present invention provide a method andapparatus for estimating a CINR in a communication system.

While the CINR estimation method and apparatus can be applied to anycommunication system, the communication system is preferably an OFDMcommunication system.

FIG. 3 is a block diagram of an MS according to an exemplary embodimentof the present invention.

Referring to FIG. 3, the MS includes an ADC 300, an FFT processor 302,and a CINR estimator 314. The CINR estimator 314 has a carrier powerestimator 304, a partial noise-interference power estimator 306, a noisepower estimator 308, a preamble code generator 310, and a CINRcalculator 312.

The ADC 300 converts a signal included in a first OFDM symbol of adownlink frame received from a BS into a digital signal. The first OFDMsymbol includes a preamble allocation available area that carries apreamble signal and an interference and noise signal.

The FFT processor 302 FFT-processes a digital preamble signal receivedfrom the ADC 300 on an OFDM symbol basis. The preamble code generator310 generates a preamble code with which to demodulate the preamblesignal.

The carrier power estimator 304 receives the FFT preamble signal fromthe FFT processor 304 and the preamble code from the preamble codegenerator 310, demodulates the FFT preamble signal with the preamblecode, and calculates a power value of the demodulated preamble signal asa carrier power value.

To be more specific, for the inputted FFT preamble signal and thepreamble code, the carrier power estimator 304 multiplies the preambletones of the FFT preamble signal by the preamble code, thus producingX[3k+seg]·C[k]. The carrier power estimator 304 calculates the complexconjugate of X[3k+seg]·C[k] and then calculates a differentialcorrelation between X[3k+seg]·C[k] and its complex conjugate. Thecarrier power estimator 304 calculates the carrier power value byextracting only the real part of the differential correlation and scalesthe carrier power value. The carrier power value can be computed by

$\begin{matrix}{P_{c} = {\frac{1}{N_{code} - 3}{Re}\{ {\sum\limits_{\underset{{k \neq 141},142}{k = 0}}^{N_{code} - 2}\; {{X^{*}\lbrack {{3 \cdot k} + {seg}} \rbrack} \cdot {X\lbrack {{3 \cdot ( {k + 1} )} + {seg}} \rbrack} \cdot {C\lbrack k\rbrack} \cdot {C\lbrack {k + 1} \rbrack}}} \}}} & (1)\end{matrix}$

where k denotes the index of a subcarrier to which a preamble tone isallocated, X[k] denotes a k^(th) FFT subcarrier, C[k] denotes an elementof the preamble code corresponding to the k^(th) subcarrier, N_(code)denotes a number of columns of the preamble code, and seg denotes anindex indicating a current segment scheme. For example, for segment 0,seg is set to 0 and for segment 1, seg is set to 1.

The partial noise-interference power estimator 306 demodulates the FFTpreamble signal received from the FFT processor 302 with the preamblecode received from the preamble code generator 310 and calculates powervalues for all of the preamble tones using the demodulated preamblesignal. The partial noise-interference power estimator 306 alsocalculates the inter-preamble tone power difference of every preambletone by comparing the power value of the preamble tone with those ofpreamble tones adjacent to the preamble tone, and calculates a finalinter-preamble tone power difference for all of the preamble tones. Thepartial noise-interference power estimator 306 also calculates a powervalue of the remaining tones except for the preamble tones. Then thepartial noise-interference power estimator 306 calculates a partialnoise-interference power value based on the final inter-preamble tonepower difference and the power value of the tones other than thepreamble tones.

FIG. 4A illustrates an operation for calculating the inter-preamble tonepower differences of preamble tones to estimate the noise-interferencepower value in the MS according to an exemplary embodiment of thepresent invention.

For notational simplicity, it is assumed that preamble tones areallocated to the first OFDM symbol of a downlink frame according to thesegment 0 scheme.

The partial noise-interference power estimator 306 calculates the powervalues of a 0^(th) subcarrier 400 and a 3^(rd) subcarrier 402 in apreamble signal in order to calculate the inter-preamble tone powerdifference of the 0^(th) subcarrier 400. Then the partialnoise-interference power estimator 306 calculates the inter-preambletone power difference of the 0^(th) subcarrier 400 by comparing thepower values.

To calculate the inter-preamble tone power difference of the 3^(rd)subcarrier 402, the partial noise-interference power estimator 306calculates the power values of the 0^(th) subcarrier 400 and a 6^(th)subcarrier 404 carrying preamble tones adjacent to a preamble tone onthe ₃rd subcarrier 402 and then calculates the inter-preamble tone powerdifference of the 3^(rd) subcarrier 402 by summing the power differencebetween the 0^(th) and 3^(rd) subcarriers 400 and 402 and the powerdifference between the 3^(rd) subcarrier 402 and the 6^(th) subcarrier404.

In this manner, the partial noise-interference power estimator 306calculates the inter-preamble tone power difference of an 849^(th)subcarrier 406. If a preamble tone is not mapped to a 410^(th)subcarrier, the partial noise-interference power estimator 306 does notcalculate the inter-preamble tone power difference of the 410^(th)subcarrier. Then, the partial noise-interference power estimator 306sums the inter-preamble tone power differences for all of the preambletones, thus creating a final inter-preamble tone power difference.

The partial noise-interference power estimator 306 also calculates apower value of the remaining tones other than the preamble tones. Thenthe partial noise-interference power estimator 306 calculates a partialnoise-interference power value using the final inter-preamble tone powerdifference and the power value of the remaining tones by

$\quad\begin{matrix}\begin{matrix}{{NI}_{par} = \frac{{\sum\limits_{\underset{i \neq {seg}}{i = 0}}^{2}( {\sum\limits_{\underset{k \neq 142}{k = 0}}^{N_{code} - 1}{{X\lbrack {{3 \cdot k} + i} \rbrack}}^{2}} )} + {NI}_{seg}}{N_{code} - 1}} \\{{NI}_{seg} = {{{{{{X\lbrack{seg}\rbrack}{C\lbrack 0\rbrack}} - {{X\lbrack {3 + {seg}} \rbrack}{C\lbrack 1\rbrack}}}}^{2}/2} - {{X\lbrack {{3 \cdot 140} + {seg}} \rbrack}}}} \\{{{{{C\lbrack 141\rbrack} - {{X\lbrack {{3 \cdot 140} + {seg}} \rbrack}{C\lbrack 140\rbrack}}}}^{2}/2} +} \\{{\sum\limits_{k = 1}^{1\; 40}\; ( {{{{2 \cdot {X\lbrack {{3 \cdot k} + {seg}} \rbrack}}{C\lbrack k\rbrack}} - {{X\lbrack {{3 \cdot ( {k - 1} )} - {seg}} \rbrack}{C\lbrack {k - 1} \rbrack}} -}} }} \\{ {{{{X\lbrack {{3 \cdot ( {k + 1} )} + {seg}} \rbrack}{C\lbrack {k + 1} \rbrack}}}^{2}/6} ) +} \\{{{{{{{X\lbrack {3 \cdot 143} \rbrack}{C\lbrack 143\rbrack}} - {{X\lbrack {{3 \cdot 144} + {seg}} \rbrack}{C\lbrack 144\rbrack}}}}^{2}/2} -}} \\{{{{{{{X\lbrack {{3 \cdot 283} + {seg}} \rbrack}{C\lbrack 283\rbrack}} - {{X\lbrack {{3 \cdot 282} - {seg}} \rbrack}{C\lbrack 282\rbrack}}}}^{2}/2} +}} \\{{\sum\limits_{k = 144}^{282}\; ( {{{{2 \cdot {X\lbrack {{3 \cdot k} + {seg}} \rbrack}}{C\lbrack k\rbrack}} - {{X\lbrack {{3 \cdot ( {k - 1} )} + {seg}} \rbrack}{C\lbrack {k - 1} \rbrack}} -}} }}\end{matrix} & (2)\end{matrix}$

where NI_(par) denotes the partial noise-interference power value,NI_(seg) denotes the final inter-preamble tone power difference, kdenotes an index of a subcarrier to which a preamble tone is allocated,X[k] denotes a k^(th) FFT subcarrier signal, C[k] denotes an element ofthe preamble code corresponding to the k^(th) subcarrier, N_(code)denotes a number of columns of the preamble code, and seg denotes anindex indicating a current segment scheme.

FIG. 4B illustrates a noise power estimation area used for estimating anoise power in the MS according to an exemplary embodiment of thepresent invention. Referring to FIG. 4B, there is a traffic allocationavailable area 410 and a preamble allocation available area 412 in anOFDM symbol 408. A traffic signal is allocated in the traffic allocationavailable area 410 and a preamble signal is allocated in the preambleallocation available area 412.

For example, when a traffic signal is carried in the OFDM symbol 408,the BS can allocate the traffic signal in the traffic allocationavailable area 410 of the OFDM symbol 408. When a preamble signal isdelivered in the OFDM symbol 408, the BS can allocate the preamblesignal in the preamble allocation available area 412 of the OFDM symbol408.

The remaining area of the traffic allocation available area 410 otherthan the preamble allocation available area 412 is referred to as anoise power estimation area 414. The noise power estimation area 414 isnot affected by a multi-path environment.

Therefore, the noise power estimator 308 estimates a noise power value,which is not affected by the effects of the multi-path environment,using the power values of tones included in the noise power estimationarea 414.

The noise power value is estimated by

$\begin{matrix}{{N = {\frac{l}{N_{traffic} - N_{preamble}}( {{\sum\limits_{k = {- L}}^{- l}\; {X\lbrack k\rbrack}^{2}} + {\sum\limits_{k = N_{preamble}}^{N_{preamble} + L}\; {X\lbrack k\rbrack}^{2}}} )}}{L = {{floor}\mspace{11mu} ( \frac{N_{traffic} - N_{preamble}}{2} )}}} & (3)\end{matrix}$

where N_(preamble) denotes a number of subcarriers allocated to thepreamble allocation available area, N_(traffic) denotes a number ofsubcarriers allocated to the traffic allocation available area, Ldenotes half of a number of subcarriers allocated to the noise powerestimation area, k denotes an index of a subcarrier to which a preambletone is allocated, and X[k] denotes a k^(th) FFT subcarrier signal.

The CINR calculator 312 calculates a CINR value based on the carrierpower value, the partial noise-interference power value, and the noisepower value received from the carrier power estimator 304, the partialnoise-interference power estimator 306, and the noise power estimator308. Specifically, the CINR calculator 312 acquires a scaled noise powervalue by multiplying the noise power value received from the noise powerestimator 308 by a boosted carrier power voltage. Then it calculates aninterference and noise power value by summing the partialnoise-interference power value and the scaled noise power value andcalculates a CINR by dividing the carrier power value by theinterference and noise power value. The CINR calculation is described as

$\begin{matrix}{{CINR} = \frac{P_{c}}{{NI}_{par} + {N( {P_{bc} - 3} )}}} & (4)\end{matrix}$

where P_(bc) denotes a boosted carrier power gain, N denotes the noisepower value, NI_(par) denotes the partial noise-interference powervalue, and P_(c) denotes the carrier power value.

FIG. 5 is a flowchart illustrating an operation for estimating a CINR inthe MS according to an exemplary embodiment of the present invention.

Referring to FIG. 5, the ADC 300 converts an OFDM symbol including apreamble signal into a digital signal and the FFT processor 302FFT-processes the digital OFDM symbol in step 500.

In step 502, the carrier power estimator 304 estimates, as a carrierpower value, the power value of the preamble signal included in the FFTOFDM symbol received from the FFT processor 302.

For example, if n preamble tones form a preamble signal, the carrierpower estimator 304 demodulates an FFT preamble signal with a preamblecode of length n received from the preamble code generator 301 andcalculates the carrier power value of the demodulated preamble signal byequation (1).

The partial noise-interference power estimator 306 receives the FFT OFDMsymbol, calculates a final inter-preamble tone power difference of thepreamble tones of the preamble signal and a power value of the othertones except for the preamble tones using the FFT OFDM symbol, andestimates a partial noise-interference power value using the finalinter-preamble tone power difference and the power values of the othertones in step 504.

For example, the partial noise-interference power estimator 306demodulates the FFT preamble signal with the preamble code, calculatesthe inter-preamble tone power differences for all of the preamble tonesthat form the demodulated preamble signal, and sums the inter-preambletone power differences, thus creating the final inter-preamble tonepower difference. The partial noise-interference power estimator 306also calculates the power values of the other tones except for thepreamble tones. The partial noise-interference power estimator 306calculates the partial noise-interference power value by summing the sumof the power values of the other tones and the final inter-preamble tonepower difference and scaling the sum according to equation (2).

In step 506, the noise power estimator 308 estimates a noise power valueusing a signal included in the noise power estimation area 414 of theFFT OFDM symbol.

For example, the noise power estimator 308 can calculate the noise powervalue of tones included in the noise power estimation area 414 of theFFT OFDM symbol by equation (3).

The CINR calculator 312 estimates a CINR using the carrier power value,the partial noise-interference power value, and the noise power value instep 508.

For example, the CINR calculator 312 calculates a final noise powervalue by multiplying the noise power by P_(bc)−3 and sums the finalnoise power value and the partial noise-interference power value,thereby creating an interference and noise power value. The CINRcalculator 312 then calculates the CINR by dividing the interference andnoise power value by the carrier power value by equation (4).

FIG. 6 is a compilation of graphs illustrating the standard deviationsand means of CINRs measured by the MS according to an exemplaryembodiment of the present invention.

Referring to FIG. 6, graphs 600 and 602 represent CINR mean values andCINR standard deviations, respectively, when the MS estimates CINRsaccording to conventional technology. Graphs 604 and 606 represent CINRmean values and CINR standard deviations, respectively, when the MSestimates CINRs according to an exemplary embodiment of the presentinvention. It is assumed herein that the CINRs are estimated in an ITU-Rchannel model with an MS's velocity of 10 km/h.

In the graph 600, the x axis represents CINRs in a real channelenvironment and the y axis represents the mean values of CINRs estimatedby the MS. A first CINR estimation performance curve can be drawn withthe CINR values on the x axis and the CINR means values on the y axis.Although the first CINR estimation performance curve has linearcharacteristics in a CINR range of approximately 0 to 15 dB on the xaxis, it loses the linearity above a CINR value of approximately 15 dB.

In the graph 602, the x axis represents CINRs in the real channelenvironment and the y axis represents the standard deviations of CINRsestimated by the MS. A second CINR estimation performance curve can bedrawn with the CINR values on the x axis and the standard deviations ofthe CINRs on the y axis. Although the second CINR estimation performancecurve converges to a certain value in a CINR range of approximately 0 to15 dB on the x axis, it fluctuates considerably above a CINR value ofapproximately 15 dB.

That is, the conventional CINR estimation results in inaccurate CINRestimates and causes errors, as the CINR values of the real channelenvironment increase. These errors increase with the CINR values of thereal channel environment.

In the graph 604, the x axis represents CINRs in a real channelenvironment and the y axis represents the mean values of CINRs estimatedby the MS. A first CINR estimation performance curve can be drawn withthe CINR values on the x axis and the CINR means values on the y axis.The first CINR estimation performance curve has linear characteristics.

In the graph 606, the x axis represents CINRs in the real channelenvironment and the y axis represents the standard deviations of CINRsestimated by the MS. A second CINR estimation performance curve can bedrawn with the CINR values on the x axis and the standard deviations ofthe CINRs on the y axis. The second CINR estimation performance curveconverges to a certain value.

That is, the CINR estimation method of the present invention enables theMS to accurately estimate CINRs even though CINRs increase in a realchannel environment.

As is apparent from the above description, exemplary embodiments of thepresent invention advantageously enable accurate CINR estimation since apartial noise-interference power value and a noise power value can becalculated even when there is no interference, when interference isnegligibly small in an actual preamble signal, or when the actual CINRof a preamble signal is large in a multi-path environment.

While the invention has been shown and described with reference tocertain exemplary embodiments of the present invention thereof, they aremere exemplary embodiments. For example, while it has been describedthat an MS is responsible for CINR estimation, a BS can estimate a CINRaccording to the present invention. Thus, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims and their equivalents.

1. A method for estimating a Carrier-to-Interference and Noise Ratio(CINR) in a communication system, comprising: generating a signal,including a traffic allocation available area for allocating a trafficsignal and a preamble allocation available area for allocating apreamble signal, by Fast Fourier Transform (FFT)-processing a receivedsymbol, the traffic allocation available area comprising the preambleallocation available area; calculating power values of preamble tonesincluded in the preamble allocation available area; calculating acarrier power value using the power values of the preamble tones;calculating a partial noise-interference power value using powerdifferences between the preamble tones and power values of remainingtones other than the preamble tones; calculating a noise power valueusing power values of tones included in a noise power estimation area,the power estimation area being an area of the traffic allocationavailable area other than the preamble allocation available area; andcalculating the CINR using the carrier power value, the partialnoise-interference power value, and the noise power value.
 2. The methodof claim 1, wherein the calculating of the partial noise-interferencepower value comprises calculating the partial noise-interference powervalue by the equation, $\begin{matrix}{{NI}_{par} = \frac{{\sum\limits_{\underset{i \neq {seg}}{i = 0}}^{2}( {\sum\limits_{\underset{k \neq 142}{k = 0}}^{N_{code} - 1}{{X\lbrack {{3 \cdot k} + i} \rbrack}}^{2}} )} + {NI}_{seg}}{N_{code} - 1}} \\{{NI}_{seg} = {{{{{{X\lbrack{seg}\rbrack}{C\lbrack 0\rbrack}} - {{X\lbrack {3 + {seg}} \rbrack}{C\lbrack 1\rbrack}}}}^{2}/2} - {{X\lbrack {{3 \cdot 140} + {seg}} \rbrack}}}} \\{{{{{C\lbrack 141\rbrack} - {{X\lbrack {{3 \cdot 140} + {seg}} \rbrack}{C\lbrack 140\rbrack}}}}^{2}/2} +} \\{{\sum\limits_{k = 1}^{1\; 40}\; ( {{{{2 \cdot {X\lbrack {{3 \cdot k} + {seg}} \rbrack}}{C\lbrack k\rbrack}} - {{X\lbrack {{3 \cdot ( {k - 1} )} - {seg}} \rbrack}{C\lbrack {k - 1} \rbrack}} -}} }} \\{ {{{{X\lbrack {{3 \cdot ( {k + 1} )} + {seg}} \rbrack}{C\lbrack {k + 1} \rbrack}}}^{2}/6} ) +} \\{{{{{{{X\lbrack {3 \cdot 143} \rbrack}{C\lbrack 143\rbrack}} - {{X\lbrack {{3 \cdot 144} + {seg}} \rbrack}{C\lbrack 144\rbrack}}}}^{2}/2} -}} \\{{{{{{{X\lbrack {{3 \cdot 283} + {seg}} \rbrack}{C\lbrack 283\rbrack}} - {{X\lbrack {{3 \cdot 282} - {seg}} \rbrack}{C\lbrack 282\rbrack}}}}^{2}/2} +}} \\{{\sum\limits_{k = 144}^{282}\; ( {{{{2 \cdot {X\lbrack {{3 \cdot k} + {seg}} \rbrack}}{C\lbrack k\rbrack}} - {{X\lbrack {{3 \cdot ( {k - 1} )} + {seg}} \rbrack}{C\lbrack {k - 1} \rbrack}} -}} }}\end{matrix}$ where NI_(par) denotes the partial noise-interferencepower value, NI_(seg) denotes the power differences between the preambletones, k denotes an index of a subcarrier to which a preamble tone isallocated, X[k] denotes a k^(th) FFT subcarrier signal, C[k] denotes anelement of a preamble code corresponding to the k^(th) subcarrier,N_(code) denotes a number of columns of the preamble code, and segdenotes an index indicating a current segment scheme.
 3. The method ofclaim 1, wherein the calculating of the noise power value comprisescalculating the noise power value by the equation,$N = {\frac{l}{N_{traffic} - N_{preamble}}( {{\sum\limits_{k = {- L}}^{- l}\; {X\lbrack k\rbrack}^{2}} + {\sum\limits_{k = N_{preamble}}^{N_{preamble} + L}\; {X\lbrack k\rbrack}^{2}}} )}$$L = {{floor}\; ( \frac{N_{traffic} - N_{preamble}}{2} )}$where N_(preamble) denotes a number of subcarriers allocated to thepreamble allocation available area, N_(traffic) denotes a number ofsubcarriers allocated to the traffic allocation available area, Ldenotes a half of a number of subcarriers allocated to the noise powerestimation area, k denotes an index of a subcarrier to which a preambletone is allocated, and X[k] denotes a k^(th) FFT subcarrier signal. 4.The method of claim 1, wherein the calculating of the CINR comprisescalculating the CINR by the equation,${CINR} = \frac{P_{c}}{{NI}_{par} + {N( {P_{bc} - 3} )}}$where P_(bc) denotes a boosted carrier power gain, N denotes the noisepower value, NI_(par) denotes the partial noise-interference powervalue, and P_(c) denotes the carrier power value.
 5. The method of claim1, wherein the received symbol comprises an Orthogonal FrequencyDivision Multiplexing (OFDM) symbol.
 6. An apparatus for estimating aCarrier-to-Interference and Noise Ratio (CINR) in a communicationsystem, comprising: a Fast Fourier Transform (FFT) processor forgenerating a signal, including a traffic allocation available area forallocating a traffic signal and a preamble allocation available area forallocating a preamble signal, by FFT-processing a received symbol, thetraffic allocation available area comprising the preamble allocationavailable area; a carrier power estimator for calculating power valuesof preamble tones included in the preamble allocation available area andfor calculating a carrier power value using the power values of thepreamble tones; a partial noise-interference power estimator forcalculating a partial noise-interference power value using powerdifferences between the preamble tones and power values of remainingtones other than the preamble tones; a noise power estimator forcalculating a noise power value using power values of tones included ina noise power estimation area, the power estimation area being an areaof the traffic allocation available area other than the preambleallocation available area; and a CINR calculator for calculating theCINR using the carrier power value, the partial noise-interference powervalue, and the noise power value.
 7. The apparatus of claim 6, whereinthe partial noise-interference power estimator calculates the partialnoise-interference power value by the equation, $\begin{matrix}{{NI}_{par} = \frac{{\sum\limits_{\underset{i \neq {seg}}{i = 0}}^{2}( {\sum\limits_{\underset{k \neq 142}{k = 0}}^{N_{code} - 1}{{X\lbrack {{3 \cdot k} + i} \rbrack}}^{2}} )} + {NI}_{seg}}{N_{code} - 1}} \\{{NI}_{seg} = {{{{{{X\lbrack{seg}\rbrack}{C\lbrack 0\rbrack}} - {{X\lbrack {3 + {seg}} \rbrack}{C\lbrack 1\rbrack}}}}^{2}/2} - {{X\lbrack {{3 \cdot 140} + {seg}} \rbrack}}}} \\{{{{{C\lbrack 141\rbrack} - {{X\lbrack {{3 \cdot 140} + {seg}} \rbrack}{C\lbrack 140\rbrack}}}}^{2}/2} +} \\{{\sum\limits_{k = 1}^{1\; 40}\; ( {{{{2 \cdot {X\lbrack {{3 \cdot k} + {seg}} \rbrack}}{C\lbrack k\rbrack}} - {{X\lbrack {{3 \cdot ( {k - 1} )} - {seg}} \rbrack}{C\lbrack {k - 1} \rbrack}} -}} }} \\{ {{{{X\lbrack {{3 \cdot ( {k + 1} )} + {seg}} \rbrack}{C\lbrack {k + 1} \rbrack}}}^{2}/6} ) +} \\{{{{{{{X\lbrack {3 \cdot 143} \rbrack}{C\lbrack 143\rbrack}} - {{X\lbrack {{3 \cdot 144} + {seg}} \rbrack}{C\lbrack 144\rbrack}}}}^{2}/2} -}} \\{{{{{{{X\lbrack {{3 \cdot 283} + {seg}} \rbrack}{C\lbrack 283\rbrack}} - {{X\lbrack {{3 \cdot 282} - {seg}} \rbrack}{C\lbrack 282\rbrack}}}}^{2}/2} +}} \\{{\sum\limits_{k = 144}^{282}\; ( {{{{2 \cdot {X\lbrack {{3 \cdot k} + {seg}} \rbrack}}{C\lbrack k\rbrack}} - {{X\lbrack {{3 \cdot ( {k - 1} )} + {seg}} \rbrack}{C\lbrack {k - 1} \rbrack}} -}} }}\end{matrix}$ where NI_(par) denotes the partial noise-interferencepower value, NI_(seg) denotes the power differences between the preambletones, k denotes an index of a subcarrier to which a preamble tone isallocated, X[k] denotes a k^(th) FFT subcarrier signal, C[k] denotes anelement of a preamble code corresponding to the k^(th) subcarrier,N_(code) denotes a number of columns of the preamble code, and segdenotes an index indicating a current segment scheme.
 8. The apparatusof claim 6, wherein the noise power estimator calculates the noise powervalue by the equation,$N = {\frac{l}{N_{traffic} - N_{preamble}}( {{\sum\limits_{k = {- L}}^{- l}\; {X\lbrack k\rbrack}^{2}} + {\sum\limits_{k = N_{preamble}}^{N_{preamble} + L}\; {X\lbrack k\rbrack}^{2}}} )}$$L = {{floor}\; ( \frac{N_{traffic} - N_{preamble}}{2} )}$where N_(preamble) denotes a number of subcarriers allocated to thepreamble allocation available area, N_(traffic) denotes a number ofsubcarriers allocated to the traffic allocation available area, Ldenotes a half of a number of subcarriers allocated to the noise powerestimation area, k denotes an index of a subcarrier to which a preambletone is allocated, and X[k] denotes a k^(th) FFT subcarrier signal. 9.The apparatus of claim 6, wherein the CINR calculator calculates theCINR by the equation,${CINR} = \frac{P_{c}}{{NI}_{par} + {N( {P_{bc} - 3} )}}$where P_(bc) denotes a boosted carrier power gain, N denotes the noisepower value, NI_(par) denotes the partial noise-interference powervalue, and P_(c) denotes the carrier power value.
 10. The apparatus ofclaim 6, wherein the received symbol comprises an Orthogonal FrequencyDivision Multiplexing (OFDM) symbol.
 11. A method for estimatinginterference and noise in a communication system, comprising: generatinga signal, including a traffic allocation available area for allocating atraffic signal and a preamble allocation available area for allocating apreamble signal, by FFT-processing a received symbol, the trafficallocation available area comprising the preamble allocation availablearea; calculating a partial noise-interference power value using powerdifferences between preamble tones included in the preamble allocationavailable area and power values of remaining tones other than thepreamble tones in the preamble allocation available area; calculating anoise power value using power values of tones included in a noise powerestimation area, the power estimation area being an area of the trafficallocation available area other than the preamble allocation availablearea; and calculating the interference and noise using the partialnoise-interference power value and the noise power value.
 12. The methodof claim 11, wherein the calculating of the partial noise-interferencepower value comprises calculating the partial noise-interference powervalue by the equation, $\begin{matrix}{{NI}_{par} = \frac{{\sum\limits_{\underset{i \neq {seg}}{i = 0}}^{2}( {\sum\limits_{\underset{k \neq 142}{k = 0}}^{N_{code} - 1}{{X\lbrack {{3 \cdot k} + i} \rbrack}}^{2}} )} + {NI}_{seg}}{N_{code} - 1}} \\{{NI}_{seg} = {{{{{{X\lbrack{seg}\rbrack}{C\lbrack 0\rbrack}} - {{X\lbrack {3 + {seg}} \rbrack}{C\lbrack 1\rbrack}}}}^{2}/2} - {{X\lbrack {{3 \cdot 140} + {seg}} \rbrack}}}} \\{{{{{C\lbrack 141\rbrack} - {{X\lbrack {{3 \cdot 140} + {seg}} \rbrack}{C\lbrack 140\rbrack}}}}^{2}/2} +} \\{{\sum\limits_{k = 1}^{1\; 40}\; ( {{{{2 \cdot {X\lbrack {{3 \cdot k} + {seg}} \rbrack}}{C\lbrack k\rbrack}} - {{X\lbrack {{3 \cdot ( {k - 1} )} - {seg}} \rbrack}{C\lbrack {k - 1} \rbrack}} -}} }} \\{ {{{{X\lbrack {{3 \cdot ( {k + 1} )} + {seg}} \rbrack}{C\lbrack {k + 1} \rbrack}}}^{2}/6} ) +} \\{{{{{{{X\lbrack {3 \cdot 143} \rbrack}{C\lbrack 143\rbrack}} - {{X\lbrack {{3 \cdot 144} + {seg}} \rbrack}{C\lbrack 144\rbrack}}}}^{2}/2} -}} \\{{{{{{{X\lbrack {{3 \cdot 283} + {seg}} \rbrack}{C\lbrack 283\rbrack}} - {{X\lbrack {{3 \cdot 282} - {seg}} \rbrack}{C\lbrack 282\rbrack}}}}^{2}/2} +}} \\{{\sum\limits_{k = 144}^{282}\; ( {{{{2 \cdot {X\lbrack {{3 \cdot k} + {seg}} \rbrack}}{C\lbrack k\rbrack}} - {{X\lbrack {{3 \cdot ( {k - 1} )} + {seg}} \rbrack}{C\lbrack {k - 1} \rbrack}} -}} }} \\ {{{{X\lbrack {{3 \cdot ( {k + 1} )} + {seg}} \rbrack}{C\lbrack {k + 1} \rbrack}}}^{2}/6} )\end{matrix}$ where NI_(par) denotes the partial noise-interferencepower value, NI_(seg) denotes the power differences between the preambletones, k denotes an index of a subcarrier to which a preamble tone isallocated, X[k] denotes a k^(th) FFT subcarrier signal, C[k] denotes anelement of a preamble code corresponding to the k^(th) subcarrier,N_(code) denotes a number of columns of the preamble code, and segdenotes an index indicating a current segment scheme.
 13. The method ofclaim 11, wherein the calculating of the noise power value comprisescalculating the noise power value by the equation,$N = {\frac{l}{N_{traffic} - N_{preamble}}( {{\sum\limits_{k = {- L}}^{- l}\; {X\lbrack k\rbrack}^{2}} + {\sum\limits_{k = N_{preamble}}^{N_{preamble} + L}\; {X\lbrack k\rbrack}^{2}}} )}$$L = {{floor}\; ( \frac{N_{traffic} - N_{preamble}}{2} )}$where N_(preamble) denotes a number of subcarriers allocated to thepreamble allocation available area, N_(traffic) denotes a number ofsubcarriers allocated to the traffic allocation available area, Ldenotes a half of a number of subcarriers allocated to the noise powerestimation area, k denotes an index of a subcarrier to which a preambletone is allocated, and X[k] denotes a k_(th) FFT subcarrier signal. 14.The method of claim 11, wherein the calculating of the interference andnoise comprises calculating the interference and noise by the equation,NI=NI _(par) +N(P _(bc)−3) where P_(bc) denotes a boosted carrier powergain, N denotes the noise power value, and NI_(par) denotes the partialnoise-interference power value.
 15. The method of claim 11, wherein thereceived symbol comprises an Orthogonal Frequency Division Multiplexing(OFDM) symbol.
 16. An apparatus for estimating interference and noise ina communication system, comprising: a Fast Fourier Transform (FFT)processor for generating a signal, including a traffic allocationavailable area for allocating a traffic signal and a preamble allocationavailable area for allocating a preamble signal, by FFT-processing areceived symbol, the traffic allocation available area comprising thepreamble allocation available area; a partial noise-interference powerestimator for calculating a partial noise-interference power value usingpower differences between preamble tones included in the preambleallocation available area and power values of remaining tones other thanthe preamble tones in the preamble allocation available area; a noisepower estimator for calculating a noise power value using power valuesof tones included in a noise power estimation area, the power estimationarea being an area of the traffic allocation available area other thanthe preamble allocation available area; and an interference and noisecalculator for calculating the interference and noise using the partialnoise-interference power value and the noise power value.
 17. Theapparatus of claim 16, wherein the partial noise-interference powerestimator calculates the partial noise-interference power value by theequation, $\begin{matrix}{{NI}_{par} = \frac{{\sum\limits_{\underset{i \neq {seg}}{i = 0}}^{2}( {\sum\limits_{\underset{k \neq 142}{k = 0}}^{N_{code} - 1}{{X\lbrack {{3 \cdot k} + i} \rbrack}}^{2}} )} + {NI}_{seg}}{N_{code} - 1}} \\{{NI}_{seg} = {{{{{{X\lbrack{seg}\rbrack}{C\lbrack 0\rbrack}} - {{X\lbrack {3 + {seg}} \rbrack}{C\lbrack 1\rbrack}}}}^{2}/2} - {{X\lbrack {{3 \cdot 140} + {seg}} \rbrack}}}} \\{{{{{C\lbrack 141\rbrack} - {{X\lbrack {{3 \cdot 140} + {seg}} \rbrack}{C\lbrack 140\rbrack}}}}^{2}/2} +} \\{{\sum\limits_{k = 1}^{1\; 40}\; ( {{{{2 \cdot {X\lbrack {{3 \cdot k} + {seg}} \rbrack}}{C\lbrack k\rbrack}} - {{X\lbrack {{3 \cdot ( {k - 1} )} - {seg}} \rbrack}{C\lbrack {k - 1} \rbrack}} -}} }} \\{ {{{{X\lbrack {{3 \cdot ( {k + 1} )} + {seg}} \rbrack}{C\lbrack {k + 1} \rbrack}}}^{2}/6} ) +} \\{{{{{{{X\lbrack {3 \cdot 143} \rbrack}{C\lbrack 143\rbrack}} - {{X\lbrack {{3 \cdot 144} + {seg}} \rbrack}{C\lbrack 144\rbrack}}}}^{2}/2} -}} \\{{{{{{{X\lbrack {{3 \cdot 283} + {seg}} \rbrack}{C\lbrack 283\rbrack}} - {{X\lbrack {{3 \cdot 282} - {seg}} \rbrack}{C\lbrack 282\rbrack}}}}^{2}/2} +}} \\{{\sum\limits_{k = 144}^{282}\; ( {{{{2 \cdot {X\lbrack {{3 \cdot k} + {seg}} \rbrack}}{C\lbrack k\rbrack}} - {{X\lbrack {{3 \cdot ( {k - 1} )} + {seg}} \rbrack}{C\lbrack {k - 1} \rbrack}} -}} }} \\ {{{{X\lbrack {{3 \cdot ( {k + 1} )} + {seg}} \rbrack}{C\lbrack {k + 1} \rbrack}}}^{2}/6} )\end{matrix}$ where NI_(par) denotes the partial noise-interferencepower value, NI_(seg) denotes the power differences between the preambletones, k denotes an index of a subcarrier to which a preamble tone isallocated, X[k] denotes a k^(th) FFT subcarrier signal, C[k] denotes anelement of a preamble code corresponding to the k^(th) subcarrier,N_(code) denotes a number of columns of the preamble code, and segdenotes an index indicating a current segment scheme.
 18. The apparatusof claim 16, wherein the noise power estimator calculates the noisepower value by the equation,$N = {\frac{l}{N_{traffic} - N_{preamble}}( {{\sum\limits_{k = {- L}}^{- l}\; {X\lbrack k\rbrack}^{2}} + {\sum\limits_{k = N_{preamble}}^{N_{preamble} + L}\; {X\lbrack k\rbrack}^{2}}} )}$$L = {{floor}\; ( \frac{N_{traffic} - N_{preamble}}{2} )}$where N_(preamble) denotes a number of subcarriers allocated to thepreamble allocation available area, N_(traffic) denotes a number ofsubcarriers allocated to the traffic allocation available area, Ldenotes a half of a number of subcarriers allocated to the noise powerestimation area, k denotes an index of a subcarrier to which a preambletone is allocated, and X[k] denotes a k^(th) FFT subcarrier signal. 19.The apparatus of claim 16, wherein the CINR calculator calculates theinterference and noise by the equation,NI=NI _(par) +N(P _(bc)−3) where P_(bc) denotes a boosted carrier powergain, N denotes the noise power value, and NI_(par) denotes the partialnoise-interference power value.
 20. The apparatus of claim 16, whereinthe received symbol comprises an Orthogonal Frequency DivisionMultiplexing (OFDM) symbol.